Wirelaying tool

ABSTRACT

A wirelaying apparatus and method using a tool ( 30 ) having a cutter ( 31 ) operatively opening a cut in the interior bore surface ( 11 ) of a cylindrical pipe fitting ( 10 ), laying wire ( 12 ) into the cut and closing the cut using a flange closer ( 33 ). The wire ( 12 ) is delivered into the cut via an aperture ( 32 ) through the cutting means ( 31 ). Delivery of the wire ( 12 ) into the cut is thereby improved, overcoming the problem of wire running free within the fitting. In a second embodiment (see FIG.  12 ) the cutter ( 31 ) is rotatably mounted allowing a double helical coil to be formed without removing the cutter from the bore surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of International Application No.PCT/GB98/03871, filed Dec. 22, 1998, and which claims priority onBritish Application No. 9727159.7, filed Dec. 24, 1997, all of which isincorporated herein by reference.

The present invention relates in general to an apparatus and method forlaying wire, and in particular but not exclusively to a tool for layingwire into the surface of a body. In a preferred embodiment, theinvention relates to a method and apparatus for laying wire into aninterior bore-surface of a pipe fitting.

Pipe fittings are commonly used to couple the ends of pipes including,for example, plastics material gas supply pipes. Such pipes must beconnected by a sealed joint so that, in use, no gas is permitted toescape through the joint.

One known method of making such a sealed joint is to engage the ends ofthe plastic pipes to be joined in a pipe fitting in the form of acylindrical sleeve. An electrical conductor is embedded in an innerbore-surface of the sleeve, usually in the form of a helical coil ofcopper wire. When an end of each pipe is positioned in the sleeve, anelectrical current is passed through the wire causing the wire to becomeheated, thereby melting the plastics material on the bore-surface of thesleeve or on the exterior surfaces of the pipes, or both. The end of thepipe thereby becomes fused or welded to the sleeve in a gas-tight sealedjoint.

EP-A-0,569,625 discloses a prior art apparatus for laying wire into theinterior bore surface of a pipe fitting, comprising a cutting tool forcutting a groove in the interior surface, a wire guide for guiding wireinto the groove, and an enclosing means for returning the cut materialback into the groove to enclose the wire.

A problem arises with the prior art apparatus and method in that aseparate tool is required for each diameter of pipe fitting, because theshape of the prior art tool closely follows the internal diameter of thepipe fitting. When the wire laying tool is used on an inappropriate sizeof sleeve, the wire is not correctly laid into the groove and insteadtends to run free inside the fitting, rendering the fitting useless.

It is desired to improve the flexibility and reliability of the priorart method and apparatus. Also, in at least a first preferredembodiment, it is desired to provide a method and apparatus for layingwire into a body having a non-constant internal diameter. That is, aninternal diameter that varies along all or part of the length of thebody, such as a reducer pipe fitting.

Further, it is desired to provide a method and apparatus for laying wireinto a body having a non-useable area, such as a side aperture of aT-shaped pipe fitting. It is desired to lay a single wire along aT-shaped pipe fitting in a helical coil at and near first and secondends thereof but avoiding the side aperture.

Further still, in another preferred embodiment, it is desired to providean improved method and apparatus for laying a double helical coil of asingle piece of wire such that the wire returns to near a startingpoint.

According the a first aspect of the present invention there is provideda wirelaying apparatus for laying wire into an interior bore surface ofa hollow cylinder, comprising: cutting means for making a cut into saidinterior bore surface; wire guide means for guiding wire into the cut;and enclosing means for closing the cut thereby enclosing the wire inthe cut; characterised in that: said wire guide means is arranged suchthat the wire enters the cut through the cutting means.

Advantageously, the wire enters the cut directly through the cuttingmeans and therefore cannot run free.

Preferably, the wire is guided through an aperture in the cutting meansideally to an exterior surface of the cutting means that, in use, facesinto the cut.

Preferably, the cutting means is arranged to produce a cut which issubstantially normal to said interior bore surface, and in the form of agroove, with said cutting means preferably lifting a flange to one sideof the cut. Ideally, the guide means guides the wire into the cut to anarea underneath the flange, and preferably a corner position underneaththe flange.

Preferably, said wirelaying apparatus comprises a wirelaying toolintegrally forming said cutting means, said wire guide means and saidenclosing means. Preferably, said tool is arranged to be carried on anelongate bar, with said wire preferably being fed along the bar,suitably by a wire delivery means such as pulley arrangement, to saidwire guide means.

The preferred embodiment is particularly intended for laying wire intothe interior bore surface of a plastics material pipe or pipe fitting.Said wirelaying apparatus is preferably arranged to receive said pipe orpipe fitting for rotation about a longitudinal axis thereof with saidwirelaying tool being held on said bar against said interior boresurface such that the pipe fitting is operatively rotated with respectto the wirelaying tool.

Preferably, the wirelaying tool is arranged such that said enclosingmeans is in a plane normal to the longitudinal rotational axis of thepipe fitting. Therefore, maximum pressure may be applied by theenclosing means to close the flap cut by the cutting means even if thetool is used with a pipe fitting having an internal diametersubstantially greater than the exterior circumference of the tool.However, the wirelaying tool is preferably arranged to have an exteriorcircumference corresponding to the interior diameter of an intended pipefitting.

Preferably, the wirelaying tool is mounted into a receiving recess insaid bar such that said tool is carried aligned with an end face and anouter circumferential face of the bar. By mounting the wirelaying toolin this position on the bar, several operational advantages areachieved. In particular, the cutting means is arranged to lie at or nearthe end of the bar. Placing the cutting tool in this position allows thecutting tool to remain in contact with the interior bore surface even ifthe internal diameter of the bore surface changes along the length ofthe pipe fitting, such as in a reducer used to couple pipes of differentdiameters.

A further advantage of the wirelaying apparatus is that the pitch of thehelical path followed by the wirelaying tool may -be changed duringwirelaying. In particular, the wirelaying apparatus may move thewirelaying tool to greatly increase the pitch of the helical path. Thisfeature is particularly advantageous, for example, in laying acontinuous piece of wire within a T-shaped pipe fitting such that thewire may be laid to avoid a side aperture of the T-shaped fitting.

According to a second aspect of the present invention there is provideda wirelaying apparatus, for laying wire into a body, said apparatuscomprising a cutting means that is rotatable about an axis substantiallynormal to an interior bore surface of said body.

The cutting means is preferably provided with a cutting face preferablyintended for making a cut, in use, by moving said cutting means throughsaid interior bore surface, in the direction of said cutting face.Advantageously, said cutting means is rotatable, such that said cuttingface is rotated about said axis. Preferably, a wire guide means guides awire through said cutting means along said axis such that said cuttingmeans rotates about said wire.

Advantageously, the cutting tool is driven in a first direction, to laywire in a first helical path, is then rotated through substantially 20°and driven to lay wire along a linear path, and then rotated through afurther 90°, to lay wire in a second helical path. Preferably, thesecond helical path lies between said first helical path such that adouble helical path is formed.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic drawings, in which:

FIG. 1 is a perspective side view of a pipe fitting;

FIG. 2 is a sectional view through the pipe fitting of FIG. 1;

FIG. 3 is a plan view of a wirelaying apparatus;

FIG. 4 is an end view of a wirelaying tool in use in a pipe fitting;

FIG. 5 is a side view of the wirelaying tool;

FIG. 6 is a front view of the wirelaying tool;

FIG. 7 is a plan view of the wirelaying tool;

FIG. 8 is a sectional side view of a preferred reducer pipe fitting;

FIG. 9 is a rear elevational view of a second preferred wirelayingapparatus;

FIG. 10 is a plan view of the apparatus of FIG. 9;

FIG. 11 is an end view of the apparatus of FIG. 9;

FIG. 12 is a cross-section view through a preferred head portion of thewirelaying apparatus of FIG. 9; and

FIG. 13 is a cross-sectional view through a preferred sleeve pipefitting having a double helical wire coil laid therein.

Referring firstly to FIGS. 1 and 2, a pipe-fitting 10 is shown in theform of a sleeve used to connect the ends of pipes such as gas pipes.The fitting 10 is hollow and generally cylindrical and has an innerbore-surface 11. Embedded in the bore-surface 11 is a helical coil ofcopper wire 12, a first end 12 a of which protrudes from a first port 13a on the exterior of the fitting 10 and the second end 12 b of whichprotrudes from a second port 13 b on the exterior of the fitting 10.

Referring also now to FIG. 2, this shows, in cross-section, a portion ofthe bore-surface 11 of the fitting 10 with the helical coil of copperwire 12 embedded therein. The turns of the wire 12 are enclosed by theplastics material of the bore-surface 11 causing the bore-surface 11 toundulate. The wire is securely retained in the bore-surface 11 and isnot prone to becoming detached, as has been the case with prior fittingsof this kind.

In use, when the fitting is required to connect two plastic pipes (notshown) the ends of the pipes are each inserted in the respective ends ofthe fitting 10. The diameter of the bore of the fitting 10 is chosen soas to be a friction fit with the pipes which it is to connect. Once thepipes are in position an electrical current is made to flow through thecopper wire 12 by appropriately connecting the ends 12 a, 12 b of thecoil to a voltage source. The passage of electrical current through thewire 12 causes the wire to become heated which heat causes the plasticmaterial surrounding the wire 12 to melt. In addition, the heat of thewire at least partially melts the outer surfaces of the pipes. After apredetermined time the current flow in the wire 12 is stopped and thepipes and the fitting are allowed to cool. The result is a weldingtogether of each pipe to the fitting 10 to produce a relatively strongjoint. Importantly, the joint is a gas-impermeable seal and so thefitting 10 can be used to sealably connect gas pipes.

Turning now to FIGS. 3 to 7, these show an apparatus for laying the wire12 in a hollow cylindrical body such as a pipe fitting 10 as shown inFIGS. 1 and 2.

Referring to FIG. 3, the wire-laying apparatus of the first embodimentcomprises a steel head portion 22, and a steel support arm 21 which isconnected to and supports the head portion 22.

Mounted on the head portion 22 is a wirelaying tool 30 and a wire supplymeans including a guide pulley 23 which supplies the copper wire 12 tothe wirelaying-tool 30 during the wire-laying process. The head portion22 has an arcuate friction surface which has been flame-hardened andpolished. The head portion may also carry a reaming cutter (not shown),such as in a position opposite to said wirelaying tool 30.

In use, a pipe fitting 10 is mounted, for example, on the spindle of acomputer-numerically-controlled CNC machine (not shown) and the supportarm 21 of the wire laying apparatus 20 is mounted in the tool-holder ofthe machine.

Optionally, a boring operation is first performed on the fitting 10,using a separate boring (reaming) cutter, or conveniently using a boringcutter carried on the head portion 22 of the wirelaying tool 20.

The CNC machine is suitably programmed to rotate the fitting 10 at afirst speed of up to about 2000 revolutions per minute, and to advancethe wire-laying apparatus into the bore of the fitting 10 withoutinitially making contact with the fitting 10.

Once the wire-laying apparatus is positioned fully inside the rotatingfitting 10, at the end at which the fitting is secured to the spindle,the wire-laying apparatus is manoeuvred so that the boring cutter ismade to cut into the inside bore-surface 11 of the fitting 10, to apredetermined depth, and the wire-laying apparatus is slowly withdrawnfrom inside the bore of the fitting at a predetermined rate, maintainingthe cutting of the bore-surface at the predetermined depth, to perform aboring operation. This ensures that the bore-surface is consistentlyeven and is smoothly cylindrical for the wire-laying operation.

Once the head portion 22 is fully withdrawn and any swarf or wastematerial has been removed, the CNC machine causes the head portion 22 tore-enter the bore of the fitting 10.

The wire-laying operation will now be described in general terms withreference to FIG. 3, and with reference to FIGS. 4 to 7 which show inmore detail the wirelaying tool 30 of the wirelaying apparatus 20.

Skilled persons in the field of CNC machines will be familiar with theconventional descriptions of X, Y and Z movements as will be referred tobelow, with Y designating movement due to rotation of a workpiecerelative to a tool, X designating movement in a horizontal plane normalto the axis of rotation of the workpiece, and Z designating movementparallel to the axis of rotation.

For the wirelaying process, the CNC machine causes the fitting 10 torotate at approximately 50 revolutions per minute and the wirelayingtool 30 is brought into contact with the bore-surface 11 of the fitting10 to cut a groove therein. The groove is substantially normal to thebore-surface 11 of the fitting 10. By moving the tool 30 at a constantrate in the direction of Z movement as represented by the arrow Z inFIG. 3, combined with constant rotational Y movement of the pipe fittingrepresented by the arrow Y in FIG. 4, a helical groove of constant pitchis formed.

Referring to FIG. 4, the preferred position of the tool 30 is shownrelative to a pipe fitting 10, with the cutter 31 engaging the interiorbore-surface 11. A flap closer 33 is arranged to lie on a plane normalto the axis of rotation of the fitting A, i.e. on the centre line of thefitting, and the cutter lies just above this centre line. Therefore, ifthe fitting 10 is exchanged for one of a larger diameter, the flapcloser still lies close adjacent the bore surface 11. The same tool canbe used to lay wire in pipes of different diameters.

As the cutter 31 of the tool 30 cuts a groove in the rotatingbore-surface 11 of the fitting 10, a flange of plastics material isdisplaced to one side of the cutter 31. The wire 12 is fed through afeed aperture 32 in the cutter 31 directly into the freshly cut groove.

The flange of displaced plastics material is guided in a directionsubstantially parallel to the direction of cutting, to meet a flapcloser surface 33 which extends across the tool 30 at an angle ofapproximately 45°. The flap closer 33 urges the flange towards theopposite side of the freshly cut groove to thereby at least partly coverthe laid wire. The flap closer 33 then presses against the displacedmaterial causing it to become heated due to friction. The result is thatthe displaced material is made to deform and enclose the wire in the cutgroove.

The boring of the bore-surface 11, immediately prior to the wire-layingoperation, provides the benefit that the bore-surface is still warm fromfriction caused by the boring cutter when the wire-laying processbegins. This assists the further frictional heating of the bore-surface11 by the flap closer 33 and by a friction surface of the head portion22 as it causes the displaced plastic material to flow over the wire,thereby embedding the wire in the freshly cut groove.

The continuous process of the wire-laying therefore involves thetemporary opening of a groove, the laying of wire in the groove, and theimmediate enclosing of the wire in the groove.

Referring to FIGS. 5, 6 and 7, the wirelaying tool will now be describedin more detail.

The wirelaying tool 30 is preferably formed by machining a single blockof material such as steel to form a cutter 31, a wire guide aperture 32,and a flap closer 33. The wire guide aperture 32 extends from a wideoval shaped opening 32 a at the top and rear of the tool 30 at an anglein the range of about 20° to 30° to emerge at an opening 32 b in a faceof the cutter 31 at the front of the tool.

The cutter 31 is provided with a first angled face 31 a leading to acutting edge, and a second angled face 31 b for directing the wireexiting opening 32 b toward a desired area of the cut, preferably astrongest corner portion. The cutter 31 is narrower in the region of thefirst face 31 a than at the second face 31 b in order to progressivelyforce the cut open.

It will be appreciated that modifications may be made to the apparatusand method without departing from the scope of the invention. Forexample a CNC machine need not be used to operate the wire-layingapparatus, although it has been found convenient to do so. In addition,the laying of the wire could begin at the end of the fitting 10 closestto the spindle of the machine, with the head portion 14 graduallyprogressing out of the bore of the fitting 10.

The operation of the wirelaying apparatus to lay wire in a pipe fittinghaving a variable internal diameter will now be described.

FIG. 8 is a sectional side view of a pipe fitting in the form of areducer having a first end 14 for receiving a pipe of a first diameter,a second end 16 for receiving a pipe of a second, smaller diameter, anda sloping section 15 therebetween. It is desired to lay a continuousstrand of wire from an inlet port 13 a to an outlet port 13 b.Previously this has not been possible because of the difficulty incorrectly laying wire into the sloping section 15.

In operation, the wirelaying tool 31 is carried on the bar 21 into thefirst end 14 of the fitting and aligned with the first port 13 a. Thebar 21 is then subject to an X axis move to drive the cutter 31 apredetermined depth into the interior bore surface 11. Next, the pipefitting is rotated in the direction of arrow Y of FIG. 8, and the tooldriven along direction Z to lay wire in a helical coil in a helicalgroove 124 of a first predetermined pitch. The first coil 124 is laidfor a predetermined distance in order to achieve a reliable gas-tightjoint in use. The coil does not continue along the entire length of thefirst section 14 of the pipe fitting 10 because the end portion of apipe introduced into the first section 14 is particularly vulnerable toover heating, causing unwanted deformation. Therefore, a cold zone isprovided by substantially increasing the rate of movement in the Zdirection to provide a second helical coil 125, having a relativelylarge pitch. Once the tool advances to a desired region of the second,smaller, section 16 of the pipe fitting 10, the drive in the Z directionis slowed to provide a third helical coil 126 in the smaller diametersection 16.

As the tool enters the sloping portion 15, an X-direction move isrequired, i.e. out of the plane of the paper of FIG. 8, in order tofollow the reducing diameter of the sloping section. Referring again toFIG. 3, it will be seen that the tool 30 is mounted in a recess at theforward end of the head portion 22 of the bar 21, such that the tool 30is the first part of the wirelaying apparatus to encounter the slopingsurface 15, and therefore the cutter 31 maintains contact with theinterior bore surface 11 throughout the sloping section 15. Since thewire 12 enters the cut directly through the aperture 32 b in the cutter31, the wire is reliably laid in the cut and does not run free insidethe fitting.

A similar method of operation is used to lay a single piece of wire in apipe fitting having a non-usable area, such as a T-shaped pipe fittinghaving a side aperture positioned approximately half way along thelength of the pipe fitting. Similar to the arrangement shown in FIG. 8,helical coils 124 and 126 are provided at either end of a T-shapedfitting, and a very large pitch helical coil 125 is used to avoid theside aperture by running the groove in the interior bore surfacesurrounding and opposite the aperture.

A second preferred embodiment of the wirelaying apparatus will now bedescribed with reference to FIGS. 9 to 13, where like reference numeralsare used for parts corresponding to the apparatus described withreference to FIGS. 1 to 8.

FIG. 9 shows a rear elevational view of the wirelaying apparatus 20having a support arm 21 carrying a head portion 22. In use, wire to belaid is carried along the support arm 21 such as by a pulley arrangement(not shown) to an aperture 23.

FIG. 10 is a plan view of the apparatus of FIG. 9, showing the aperture23 passing through the head portion 22 from an entry 23 a to an exit 23b.

FIG. 11 is a end view of the apparatus FIGS. 9 and 10, and FIG. 12 is asectional view through the head portion 22.

As shown more clearly in FIGS. 11 and 12, the head portion 22 isprovided with a curved forward facing pressure or friction surface 24intended to lie in use against the interior bore surface 11 of a pipefitting, as in the first embodiment.

A hollow shaft 25 is provided in the aperture 23 having a splined end 25a which acts as a pinion arranged to be engaged with a rack 26 carriedon the support arm 21. Longitudinal movement of the rack 26 rotates thehollow shaft 25 within the aperture 23.

A cutter 31 is provided at a forward end of the shaft 25 protruding fromthe exit 23 b of aperture 23. The cutter 31 is preferably non-rotatablyreceived within the interior end 25 b of the shaft 25, to rotate withthe shaft 25, such as a square cross-section fitting into acorresponding square recess. The rack 26 and pinion 25 a arrangement isconveniently sized so as to fit within the confines of the support arm21 and head 22 and thus fit within a pipe fitting, but any othersuitable rotation arrangement may be employed.

In use, a wire 12 to be laid is guided through the hollow centre of theshaft 25, conveniently using a ceramic disc 27 at the entry thereof toreduce friction. The wire 12 passes through the central longitudinalwire guide aperture 32 of cutter 31, to emerge from the cutter 31directly into the freshly cut groove. Conveniently, the cutter 31 may berotated about the wire 12, such that the wire may be laid in a groovewhich changes direction whilst the cutter 31 is engaged in the boresurface 11 of the fitting 10.

The exit 23 b of the aperture 23 is provided with a plate 28 having aplurality of flap closers 33 mounted thereon or formed therein. The oreach flap closer 33 is arranged to lie rearwardly in the direction ofcutting from the cutter 31.

Referring now to FIG. 13, a preferred method of operation of theapparatus shown in FIGS. 9-12 will now be described.

FIG. 13 shows a section of a pipe fitting 10 where it is desired to laya single continuous piece of wire 12 in a double helical path from aninput port 13 a to an output port 13 b. This arrangement findsparticular application, for example, when it is desired to provide morethan one coil arrangement in a pipe fitting so that joints may be madeseparately, conveniently at different points in time. The double helicalcoil arrangement may be used with any form of pipe fitting, including asleeve, reducer, T-shaped, elbow or cap-end pipe fitting.

With reference in particular to FIG. 12 and FIG. 13, the cutter 31 isset to a first direction and driven by suitable X and Z movement of thesupport arm 21 through the interior bore surface 11 of the pipe fitting10 which is rotated past the cutter 31, such that wire 12 is laid in afirst inward helical coil 121.

At the end of the first helical coil 121, the rotation of the fitting 10and the movement of the head 22 and arm 21 is stopped. That is, atposition 121 a of FIG. 13. The cutter 31 is then rotated by means of therack 26 and the pinion 25 a through about 90° to a second desiredcutting direction. The wire 12 is laid in the second direction in alinear path without the fitting 10 being rotated, to form a connectingportion 122. The connecting portion is ideally of a length correspondingto one half of the pitch of the first helical coil 121. The tool 31 isthen rotated again to a third cutting direction, preferably throughabout 90° such that the tool has rotated through about 180° from thefirst cutting direction. By rotating the fitting 10 in the reversedirection and performing a movement in the reverse Z direction of thehead portion 22, the cutter 31 scribes a second helical path 123 fromthe position 123 a to the outlet port 13 b.

The present invention extends to cover the embodiments of the wirelayingapparatus and the methods of operation of the wirelaying apparatus, asdescribed above, and the pipe fittings produced by said apparatus andmethods. The invention extends in particular to the wirelaying tool 30having a wire guide aperture therethrough for delivering wire directlyin to the cut.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s) The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

What is claimed is:
 1. A wirelaying apparatus for laying wire into aninterior bore surface of a hollow cylinder, comprising: a cutting toolhaving a cutter for making a cut into the interior bore surface; wireguide means for guiding wire into the cut; and enclosing means forclosing the cut thereby enclosing the wire in the cut; characterized inthat: the wire guide means comprises an aperture extending through thecutting tool to an exterior surface of the cutter lying in the cut inuse such that the wire enters the cut directly through the cutter,wherein the cutter is rotatable around the aperture guiding the wire. 2.A wirelaying apparatus, for laying wire into an interior bore surface ofa hollow cylinder, comprising: a cutting tool having a cutter for makinga cut into the interior bore surface; wire guide means for guiding wireinto the cut; and enclosing means for closing the cut thereby enclosingthe wire in the cut; characterized in that: the wire guide meanscomprises an aperture extending through the cutting tool to an exteriorsurface of the cutter lying in the cut in use such that the wire entersthe cut directly through the cutter, wherein the cutter is operativelyrotatable about an axis substantially normal to the interior boresurface.
 3. A wirelaying apparatus as claimed in claim 2, wherein thecutter comprises a cutting face for operatively making a cut through theinterior bore surface in the direction of the cutting face, and whereinthe cutting means is rotatable such the that the cutting face is rotatedabout the axis.